1. Field of the Invention
The invention relates to a method of redundancy-reducing coding of the values of picture elements of pictures which are scanned line-by-line and which are distributed in a matrix into lines and picture elements, the difference value being formed for substantially each picture element between the actual value of the picture element and a predictive value obtained from the values of other picture elements, as well as to a digital circuit for implementing the method.
2. Description of the Prior Art
The redundancy reduction is effected by means of predictive decorrelation of picture elements. Such methods are, for example, disclosed in German published patent application No. 2312 526 and constitute a general form of DPCM (differential pulse code modulation). This enables a considerable data reduction without a significant loss in information when storing and transmitting pictures respectively. The known DPCM methods, however, have the drawback relative to other transformation methods that the prediction is performed, causally, that is to say during scanning the previously scanned value is involved in the prediction and the reconstruction relates each time to the values which have already been construed. The prediction itself cannot relate to the entire picture area but only the preceeding picture area which preceded during decorrelation with subsequently scanned picture elements is not known.